Within the machining art, the desirability of providing an automatic machine tool capable of accurate machining of blind or internal slots in a hollow workpiece is well known. Blind slots are used, for example, in the hydraulic control field for fluid porting. Typically, these slots are situated along the side of an internal bore, or the like. The slots must be machined independently of the bore, adding to the complexity of the manufacturing operation.
U.S. Pat. No. 4,154,145 to Bishop discloses a typical prior art bore slotting machine. The apparatus disclosed is quite complex, including several cams, associated cam followers and reduction gears. As is well known, the inherent complexity of this device is a distinct disadvantage due to the relatively large power requirements for operation and the problem of wear in all of the mechanical parts and connections. These shortcomings provide decreased operating efficiency of the machine and greatly limit its overall utility. Nonetheless, this machine is the most popular machine on the market for this function.
A recent attempt at producing a simplified slot forming machine is disclosed in Japanese Patent Publication No. 59-115112 Sawada, published July 3, 1984. This machine includes a cam to impart a reciprocating motion to a slotting tool. The tool is retained within a pivotal slide body mounted on a spring. The depth of the cut is controlled by the position of a cam follower adjusted by a hydraulic cylinder. Although somewhat effective, this device does not address the problem of providing high quality slots of close tolerances, especially in harder metals. The spring mounting tends to allow for the possibility of tool chatter, especially at high production speeds, thereby decreasing the efficiency of the cutting operation. This tendency mostly occurs as the tool makes its forward and upward stroke; i.e. the pivoting movement of the slide body being resisted at this point only by the counteracting spring.
A need exists therefore for an improved blind slot forming apparatus which is relatively simple, thus avoiding the complexities of the prior art, while providing a smooth, consistent cutting action at production speeds.